1. Field of the Invention
This invention relates generally to a tape cassette of the type in which detecting holes with respective obstruction or indicating members are provided in the bottom of the cassette casing so as to make it possible to retrieve or determine information as to the tape cassette and the tape therein. The invention has particular, though not exculsive application, to a tape cassette for a video tape recorder.
2. Description of the Prior Art
It is known to provide tape cassettes for video tape recorders wherein detecting holes with respective obstruction or indicating members are provided in the bottom wall of the tape cassette casing so as to make it possible to retrieve or determine information therefrom as to the tape cassette and the tape therein, such as information as to the kind of tape, the thickness of tape and the like, and further to achieve the prevention of erroneous erasure.
In a tape cassette of the described kind, each of the detecting holes is opened or is closed by means of the respective obstruction member beforehand on the basis of predetermined information, and when the tape cassette is mounted in the video tape recorder, such predetermined information is retrieved by detecting pins provided in the video tape recorder in order to detect whether the respective detecting holes are opened or are closed by the obstruction members. More particularly, if the detecting hole is closed, the detecting pin abuts against the obstruction member and is lowered against the force of a resilient member or material, and if the detecting hole has been opened, the detecting pin is fitted into the detecting hole and is unaffected, so that the necessary information is retrieved with reference to any change in the height of the detecting pin.
Accordingly, the detecting hole must have a depth sufficient to receive the detecting pin and, if the obstruction member is also moved up and down along the detecting hole as in the prior art, the detecting hole must also have a depth sufficient to accommodate the stroke of the obstruction member. Thus, the detecting holes with respective obstruction members must be disposed only in those limited spaces free from the other necessary parts accommodated in the tape cassette, such as, the tape, tape reels, tape guides, various mounting pins and so on. In the prior art, detecting holes with the obstruction members have been provided within a triangular space located just to the rear of a central portion of a trapezoidal bottom opening or cutout in the bottom wall of the cassette casing so as to avoid interference with the tape reels.
Recently, there has been a tendency to increase the necessary information as to the tape cassette and the tape therein, so that it has become necessary to provide as many as possible of the detecting holes with respective obstruction members in the bottom wall of the cassette casing. However, there is a limitation on increasing the number of detecting holes as mentioned above.